1. Field of the Invention
The present invention relates to a connecting structure for connecting a flexible printed circuit board to another printed circuit board, in which patterns are aligned to allow the printed circuit boards to be connected by soldering.
2. Description of the Prior Art
In one conventional connecting structure patterns 104 on a flexible printed circuit board 103 are aligned with patterns 102 on a printed circuit board 101 and the patterns 102 and 104 are connected by soldering 105, as shown in FIG. 3. However, the patterns 104 on the flexible printed circuit board 103 are manually aligned with the patterns 102 on the printed circuit board 101, resulting in a problem in that hand movement, etc. can make the positioning and therefore the connection between the patterns 102 and 104 by the soldering 105 difficult.
In FIG. 4 is shown a first prior art connecting structure for flexible circuit boards in which a plurality of longitudinal slits 212 are provided in one end portion of a flexible circuit board 210 to form portions 213 outboard of the slits 212 which are bent and are inserted into engaging holes 211d formed in a rigid circuit board 211 to position conductor patterns 210b on the flexible circuit board 210 against conductor patterns 211b on the rigid circuit board 211 (refer to Japanese Utility-Model Laid-Open Publication No. Sho 61-114877 for example).
However, the above connecting structure suffers from a problem in that when the flexible circuit board 210 is lifted upward, the bent portions 213 can easily be removed from the engaging holes 211d. 
FIGS. 5 (a) and 5 (b) show a second prior art structure for connecting conductive members which includes an engaging hole 303 in a circuit board 301. One end of a flexible circuit board 302 is divided into three portions by making two slits 305, and the central portion 306c is bent downward, with first and second engaging portions 306a and 306b positioned on the upside surface of the circuit board 301. The third (central) engaging portion 306c is bent to be positioned on the underside surface of the circuit board 301, i.e. the third engaging portion 306c is passed under the circuit board 301 through the engaging hole 303 so that the flexible circuit board 302 is fixed to the circuit board 301 in a sandwiched manner, and connecting parts 307 at the end portion of the flexible circuit board 302 are connected to electrode patterns 304 on the circuit board 301 by soldering 308 (refer to Japanese Patent Laid-Open Publication No. 2002-270978 for example).
However, the arrangement described above suffers from a problem in that part of the electrode patterns 304 must be formed on the underside surface of the circuit board 301, that is, the circuit board 301 must be double-sided.
FIGS. 6 (a) and 6 (b) show a third prior art connecting structure which includes an engaging hole 403 in a circuit board 401. The vicinity of one end portion of a flexible circuit board 402 is bent perpendicularly to the extended direction over the entire width to provide a convexly projecting engaging portion 405. The engaging portion 405, which has a height greater than the thickness of the circuit board 401, comprises a projecting portion 406a having a width equal to or smaller than the lateral width of the engaging hole 403 and a lock portion 406b formed on the top of the projecting portion 406a and having a width greater than the lateral width of the engaging hole 403. Thus, once the engaging portion 405 is fitted into the engaging hole 403, the lock portion 406b is caught on the edge of the engaging hole 403 so that the flexible circuit board 402 is fixed to the circuit board 401. Then, connecting parts 407 in the end portion of the flexible circuit board 402 are connected to electrode patterns 404 on the circuit board 401 by soldering 408 (refer to Japanese Patent Laid-Open Publication No. 2002-270979 for example).
However, the arrangement above suffers from a problem in that the engaging portion 405 should be formed projecting downward from the flexible circuit board 402, which complicates the shape of the flexible circuit board 402.